R. Pérez-Álvarez

A simple model for delta‐doped field‐effect transistor electronic states

We propose a simple potential model which reproduces the main properties of the electronic structure of a delta‐doped field‐effect transistor. On the basis of selfconsistent calculations we conclude that the energies, wavefunctions and other characteristic properties obtained with the proposed model are very close to the results of full selfconsistent calculations.

Some elementary questions in the theory of quasiperiodic heterostructures

The characterization of the spectrum of eigenstates of quasiperiodic heterostructures is discussed by focusing on three questions. Arguments are advanced to justify the often indiscriminate use of different approximants in the calculation of the eigenvalue spectra. It is stressed that the calculation of the fractal dimension may be rather inaccurate if the high eigenvalue range is not included, even if physically the interest is limited to the low range. The question of self-similarity is critically examined and found to have a very limited range of validity in practice. The unique properties of the Rudin-Shapiro sequence are also stressed.

Simultaneous surface Green function matching for N interfaces

The method of surface Green function matching (SGFM) is extended to the case of an arbitrary number N of interfaces so that all the SGFM formulae are obtained in a compact N*N matrix (or supermatrix) form ready for practical calculations. As an example, shear (surface horizontal) waves in a Ni-W-Al-Ni structure are studied by a straightforward application of the general formulae. The range of applications of physical interest is stressed.

Long-wavelength polar optical modes in GaAs semiconductor layered structures

A long-wavelength model of polar optical modes coupling the vibration amplitude u (the relative displacement vector) and the electrostatic potential phi leads to a system of coupled differential equations. This system is here solved for a quantum well without approximations and with simultaneous satisfaction of mechanical and electrostatic matching boundary conditions. Explicit solutions for u and phi are given, and the resulting eigenmodes for GaAs-based quantum wells are studied in detail. The model gives modes with a mixed character describing the coupling between u and phi . Thus one single model yields confined quasi-longitudinal (strictly longitudinal for in-plane wavelength vector kappa =0), confined quasi-transverse (strictly transverse for kappa =0) and interface modes. The dynamical structure, spectral strength and spatial dependence of the relevant amplitudes are studied in detail. The results are in good agreement with available Raman experimental data and have all the basic features present in microscopic calculations. Some comments are made on the limitations of purely dielectric or purely mechanical models.

Electronic structure of delta-doped quantum well as a function of temperature

We report on the electronic structure of a delta-doped quantum well of B in Si as a function of temperature from 0 K to room temperature. The calculation is carried out self-consistently in the framework of a Hartree approximation. The energy levels and the occupation number of the discrete states is reported. We conclude that the temperature is not an important factor below 60 K. If temperature is greater than 80 K the level positions are shifted but the changes in carrier concentration are not significant. We give a possible qualitative explanation of the widths of the intersubband absorption peaks.

Some properties of the elastic waves in quasiregular heterostructures

The normal-mode spectrum of quasiregular structures has peculiar properties which have stimulated a great deal of research. The current situation is critically examined for the case of elastic waves. So far most of the research in this field appears to be theoretical. The roles of boundary conditions and of the constitutive material blocks are discussed, as well as the conditions required for reliable calculations of the topological properties of the spectra. The different quasiregular sequences more commonly studied may have significantly different formal properties, a fact not often considered. The relationship to other fields of physics is pointed out, the need for more experimental work is stressed, and, generally speaking, some directions for further research in the field are suggested.

Relations between Transfer Matrices and Numerical Stability Analysis to Avoid the

The transfer matrix method is usually employed to study problems described by

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Problem

equations of matrix Sturm--Liouville (MSL) kind. In some cases a numerical degradation (the so called

Polar optical modes in GaAs-AlAs superlattices

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